Arc plasma torch with same liquid cooling means for electrodes



ARC PLASMA TORCH WITH SAME LIQUID COOLING MEANS FOR ELECTRODES FiledApril e, 1966 Aug; 26, 1969 e. FuKslEwlcz 2 Sheets-Sheet 1 EdmundFuksewicz INVENTQR ARC PLASMA TORCH WITH SAME LIQUID COOLING MEANS FORELECTRODES Filed April 6, 1966 Aug. 26, 1969 E. FuKsn-:wlcz

2 Sheets-Sheet 2 Eclruncl Fuksiewicz INVENTOR.

BY g bw fw Attorney Fig.

United States Patent O U.S. Cl. 313-32 5 Claims ABSTRACT F THEDISCLOSURE Plasma torch with an electrode assembly in a generallycylindrical housing having channels for the circulation of a coolingfluid and for the admission of a gas, the assembly including a hollowstem seated in the housing through the intermediary of a resinous layer,a generally cupshaped cathode structure engaging the open end of thestem, a nozzle-shaped anode confronting that structure and a guide ringfor the gas flow contacting the anode but separated from the cathodethrough an interposed insulating spacer; water admitted through the stemilows through a feeding tube into the cathode structure, then passesthrough a duct within the layer into a channel of the housing whichopens toward the anode, and leaves via another housing channel.

My present invention relates to a direct-current-arc plasma torch, aso-called plasmatron, destined especially for cutting various materials,particularly metals, by means of a plasma jet from any gas.

As known, hitherto used plasma torches essentially consist of twoelectrodes, i.e. a cathode and an anode which are fixed in a specialbody constituting the housing of the torch. The torches operate in sucha manner that into the electric arc, produced between the saidelectrodes, gas is introduced under pressure which under the action ofthe high temperature of the arc is converted into a plasma jetconstituting the cutting agent.

In conventional constructions of such torches, the cathode is xed in aspecial housing which in turn is fastened to an elongate stem. The anodeis constituted by a metal nozzle.

On account of the high temperature of the plasma, the component parts ofthe torch, especially the cathode together with its holder and theanode, require intensive cooling. As there exists simultaneously thenecessity of electrically insulating the two electrodes from oneanother, the cooling has heretofore been effected by the circulation ofa cooling medium by way of outer liquid conduits made of insulatingmaterial.

Such a cooling system exhibits, however, the disadvantage that itrequires special connector pipes for feeding and carrying off thecooling medium which complicates the construction of the torch and itsoperation.

On the other hand, owing to the presence of several replaceable elementsin the body constituting the outer housing, prior torch constructionsgave rise to some difliculties in obtaining the required elect-ricinsulation and the proper iluidtightness in the circulation system forthe cooling medium.

The object of my present invention is to provide a torch of this typewhich is free from the above-mentioned inconveniences and which affordsthe required insulation of its electrodes and iluidtightness of itscooling system. This object is realized by the torch according to theinvention. It comprises, like known torches, a body in which all thecomponent parts are fixed, more specifically a tubular stem, having acathode indirectly seice cured thereto through a holder, and aconfronting anode in the form of a nozzle.

For the purpose of illustrating a preferred embodiment, a torchaccording to the invention is schematically shown in the accompanyingdrawing in which:

FIG. 1 is a longitudinal section of the torch, the cooling system beingexposed;

FIG. 2 is another longitudinal, section showing the way of the gas flow;and

FIGS. 3 and 4 are enlarged sectional views showing alternate jointsbetween the cathode holder and the tubular stem.

The torch according to the invention has a tubular stern 1 fastened in agenerally cylindrical housing 5 by a tight joint including a layer 15 ofcast synthetic resin, a replaceable holder 3 for a cathode 14 beingaxially pressed onto the core 1 by an insulating spacer 11 overlying aring 9 and a replaceable nozzle 6 which constitutes the anode.

As illustrated in FIG. 3, the cathode 14 may be supported on anelectrode body 3 forming a frustoconical seat for the beveled end of astem 1'. In the assembly shown in FIGS. 1, 2 and 4, however, the holder3 is received in a cylindrical bottom recess of stem 1 withinterposition of an O-ring 17 between the holder and the peripheral wellof this recess.

The construction of the torch according to the invention, thecirculation of the cooling medium and the way of the gas flow aredescribed below in a more detailed manner by way of example.

The cooling water is supplied to the torch through the stem 1 and flowsthen through a feed pipe 2 into the generally cup-shaped body 3 servingas a holder for the cathode. The body 3 or 3 is sealed to the stern 1 or1 by the conical joint of FIG. 3 or by the use of a selftighteningrubber O-ring as shown in FIGS. l, 2 and 4. From the body 3 supportingthe cathode 14, the water flows through the space existing between thepipe 2 and the stem 1 to and through a discharge pipe 4, thereafterthrough a longitudinal channel 18 in the housing 5, closed by a plug 27,into an outer peripheral groove 25 of nozzle 6 and, after washing aroundsaid nozzle, through another longitudinal channel 19 and through anipple 7 outwardly. The nozzle 6 constituting the anode of the torch issealed by means of two self-tightening rubber O-rings 20, 21 contactingthe inner wall surface of housing 5 above and below the ring space 25.The assembly is completed by a retaining cap 16 engaging a threadedflange 26 of the housing, thus holding the anode structure 6, 9, thespacer 11 and the cathode structure 3, 14 in position.

The stem 1 is electrically insulated from the housing 5 by theintervening layer of cast synthetic resin 15. The pipe 4 is made ofinsulating material.

The gas is supplied to the torch through a nipple 10, FIG. 2, mountedlike the nipple 7 on the periphery of housing 5, and through anotheraxially extending channel 22 in the housing, whereupon the gas isconveyed to a gas chamber 23 in the ring 9 shaping the flow, this ringhaving entrance ports 24 which open tangentially onto its inner surfaceto cause a whirling of said gas which is then introduced into the spaceexisting between the cathode holder 3 and the nozzle 6.

The gas may also be introduced axially if the entrance ports areinclined in relation to the axis of the torch.

The torch is placed in operation upon ignition of the electric arcbetween the electrodes 6, 14 which generally takes place after actuationof thhe systems for supplying the cooling medium and the gas.

3 I claim:

v 1. A plasma torch comprising a generally cylindrical unitary housingformed in its peripheral wall with axially extending channels for thecirculation of a cooling fluid; a tubular stem extending axially intosaid housing from one end thereof; means including a layer ofnonconductive material between said housing and said stem for securingsaid stem to said housing in electrically insulated relationshiptherewith; a cathode structure having a generally cup-shaped body influidtight contact with said stem in said housing; a feeding tubedisposed in said stem with annular clearance and extending yinto saidbody for admitting into same a stream of cooling uid introduced intosaid stem; an anode structure including a nozzle-shaped electrodedisposed in said housing at the other end thereof and confronting saidcathode structure, said anode structure further including a guide ringspacedly surrounding said cathode structure to form a gas chambertherewith; an insulating spacer interposed between said guide ring andsaid cathode structure; retaining means at said other end of saidhousing for holding said anode structure, said spacer and said cathodestructure in position; and conduit means for admitting a gas to saidchamber; said nozzle being provided with an outer peripheral grooveforming a ring space within said housing communicating with saidchannels, said layer having a passage connecting one of said channelswith said annular clearance for conveying cooling uid from said body tosaid ring space whence the uid is discharged through another of saidchannels; said layer, spacer, guide ring and nozzle axially abutting oneanother under pressure of said retaining means along the inner wallsurface of said housing, said channels terminating at the bottom of saidinner wall surface in lateral ports at the level of said ring space.

2. A plasma torch as defined in claim 1 wherein said conduit meansincludes a further axial channel in the peripheral wall of said housing.

3. A plasma torch as defined in claim 1 wherein said layer consists ofcast synthetic resin.

4. A plasma torch as dened in claim 1 wherein said stem has a beveledend, said body forming a frustoconical seat for said beveled end.

5. A plasma torch as defined in claim 1 wherein said stem has acylindrical recess, said body being partly received in said recess,further comprising an O-ring interposed between said body and theperipheral wall of said recess.

References Cited UNITED STATES PATENTS 2,960,594 11/1960 Thorpe 219--753,294,953 12-1966 Spies 219-121 3,375,392 3/1968 B'rZOZoWski et al.313-231 3,116,405 12/1963 Browning et al. 313-231 X 3,198,932 8/1965Weatherly 219-75 X 3,309,492 3/1967 Fields 219-75 ROBERT SEGAL, PrimaryExaminer P. C. DEMEO, Assistant Examiner U.S. Cl. X.R.

